Field of the Invention
The present invention relates to electronic devices, and more particularly, to an antenna structure and an electronic device comprising the antenna structure.
Description of the Prior Art
In general, radio frequency signals operate by linear polarization or circular polarization; hence, radio frequency signals undergo polarization in a way conducive to their application. For instance, all the electromagnetic waves of the positioning signals defined pursuant to the regulations of global positioning systems (GPS) usually operate by circular polarization. To receive the positioning signals operating by circular polarization, the signal receiving end is equipped with an antenna operating by circular polarization, such as a patch antenna or a ceramic antenna, so as to receive and send the positioning signals efficiently. Both the two aforesaid antennas are close to perfect circular polarization but have narrow inherent bandwidth and narrow circular polarization bandwidth. The two aforesaid antennas will still meet bandwidth requirements, if the received positioning signals are merely applied to the aforesaid GPS. However, if the received positioning signals are applied to both the aforesaid GPS and global navigation satellite systems (GNSS), the bandwidth provided by the two aforesaid antennas will be inadequate.
Moreover, ceramic antennas are made of ceramic materials of high rigidity, whereas the bandwidth of patch antennas is narrow, and in consequence antenna designers find it difficult to fine-tune the receiving and sending frequencies. Both patch antennas and ceramic antennas take up much area when mounted in place. Furthermore, although conventional PIFA has wide signal receiving and sending bandwidth, it involves linear polarization of electromagnetic waves rather than circular polarization of electromagnetic waves. Hence, the prior art is not only confronted with the trend toward downsized electronic devices, but is also required to mount a circularly polarized and compact antenna on ever-diminishing electronic devices.